Selective adsorption of phosphate by 2D thin-bladed ZIF-L in phosphate mining wastewater: An investigation of single phosphorus and phosphorus-chromium composite systems

The Yangtze River basin is the primary region for phosphate resource distribution in China, and pollution from phosphorus and chromium during phosphate mining poses a significant danger to the local water environment and soil safety. 2D ZIF-L, a novel zinc-based ZIF material, demonstrates substantial potential for water pollution remediation owing to its distinctive leaf-like shape and superior hydrophilicity. Currently, there are no reports regarding the research of this substance inside the phosphorus-chromium composite pollution system. This paper presents the preparation of ZIF-L materials exhibiting superior synergistic adsorption capabilities for phosphorus and chromium, utilising zinc nitrate as the zinc source and 2-methylimidazole as the organic ligand through a precipitation method under conditions of low molar ratio and low water usage, achieving a saturated phosphorus adsorption capacity of 192.9 mg/g. Acidic conditions enhanced the removal of phosphorus and chromium by ZIF-L; the initial concentration of phosphorus was a key factor in determining the ability of chromium to inhibit or promote the total adsorption capacity of ZIF-L; and the presence of chromium augmented the adsorption rate of phosphate by ZIF-L. The adsorption of phosphate by ZIF-L in the single phosphorus/phosphorus-chromium composite contaminated solution was consistent with the Langmuir model and the quasi-second-order kinetic model, which belonged to the adsorption of a monomolecular layer and was dominated by chemical adsorption. The adsorption mechanism primarily involved both electrostatic attraction and ligand exchange. To summarise, ZIF-L has extensive potential for remediating phosphate mining pollutants.